As an electro-photographic type image forming apparatus, a printer including a photosensitive body and a developing device configured to supply toner to the photosensitive body is known.
A conventional printer is provided with a detection device for detecting information on a developing cartridge assembled therein, for example, for detecting whether or not the cartridge is a brand new cartridge.
In a laser printer proposed in Japanese patent application publication No. 2006-267994, a detection gear is rotatably provided on a developing cartridge. A contact protrusion is provided on the detection gear for contacting an actuator in a main casing of the laser printer. When the developing cartridge is assembled to the main casing, the detection gear is driven to rotate so that the contact protrusion permits the actuator to pivotally move. A photo-sensor detects this pivotal movement of the actuator, enabling the laser printer to acquire information on the developing cartridge based on the detection results.